| 摘要 |
Process for treatment and bleaching of pulp, comprises: (A)cooking pulp; (B) opt. oxygen delignification to reduce kappa value to less than 24 (14); and (C) acid treatment at 75-130 deg. C and pH 2-5 to reduce kappa value by 2-9 units. In order to prevent pulp storage life being reduced dwell time (t) in treatment tower for (C) is 30-300 mins., min. treatment temp. (Tmin. deg. C) is given by equation Tmin = 10517/(24 +ln (2t)) (I) and max. treatment temp. (Tmax deg. C) is given by equation Tmax = Tmin + 23 degC (II). Addn. and/or removal of pulp from tower is controlled to maintain even flow conditions in tower and keep pulp dwell time constant. The following are also claimed: (i) use of step (C) in any of the following (partial) bleaching sequences: K-O-AD-ZD, K-O-ADN-D, K-O-AD-D, K-O-ADQ-Op-D, O-ADQ-Op-ZD, K-O-ADQ-P, K-O-AD-Op-D, K-O-AD-Op-ZD, K-O-AD-P, K-AD-ZD, K-ADN-D, K-AD-D, K-ADQ-Op-D, K-ADQ-Op-ZD, K-ADQ-P, K-AD-Op-D, K-AD-Op-ZD, K-ADQ-P, K-AD-Op-D, K-AD-Op-ZD, K-AD-P, K-O-AQ-ZDQ-P, K-O-A-ZD-P, K-O-A-O-D, K-OP-A-O-ZD, K-O-A-Z-D, K-O-A-ZD, K-AQ-ZDQ-P, K-A-ZD-P, K-A-O-D, K-A-O-ZD, K-A-Z-D, K-A-ZD, K-O-AQ-ZQ-P, K-O-AQ-P, K-O-AQ-O-ZQ-P, K-AQ-ZQ-P, K-AQ-P or K-AQ-O-ZQ-P (A = high temp. acid treatment step (C), AQ = acid treatment with addn. of chelating agent, D = ClO2 treatment, Dn = ClO2 treatment/neutralisation step, K = cooking, O = O2 delignification, Op = peroxide/O2 treatment step, P = peroxide treatment, Q = chelating agent treatment, Z = O3 treatment and ZQ = O3 treatment with addn. of chelating agent); and (ii) appts. for carrying out step (C). |
